Born to run? Associations between gestational and early-life exposures and later-life performance outcomes in Thoroughbreds.
Abstract: Gestational and early-life exposures may modulate development during growth and influence future athletic performance. Objective: To investigate associations between gestational and early-life exposures in Thoroughbreds and (i) likelihood of racing, (ii) total number of runs and (iii) total prizemoney by the end of the 3-year-old year. Methods: Prospective cohort. Methods: Daily records were kept on the location and duration of turnout, management and veterinary-attended episodes of disease or injury from birth until leaving the farm or study exit for 129 Thoroughbred foals on six stud farms. Dams' signalments, reproductive and gestational health records were collated concurrently. Available race performance records to the end of the fourth year of life were collected from industry databases. Mixed effects logistic and linear regression modelling, including farm, mare and stallion as random effects, were used to investigate associations between gestational and early-life exposures and race performance outcomes. Results: Overall, 76% (98/129, 95% CI: 68-82) of horses raced, making a median of 7 starts (IQR 4-11, range 1-23) and earning a median of £6898 (IQR 1712-17,987; range 0-197,601) in prizemoney. Increasing average daily turnout time (hours) and turnout area (acres) in the first 6 months of life were associated with increased odds of racing and increased total prizemoney earned, respectively (OR 1.31, 95% CI: 1.09-1.58 p = 0.004 and β-coefficient = 0.32 (lnGBP), 95% CI: 0.03-0.61, p = 0.03). Age at weaning (days) was associated with increased odds of racing and an increased total number of runs (OR 1.03, 95% CI: 1.01-1.05 and β-coefficient = 0.09, 95% CI: 0.04-0.14, p < 0.05, respectively). Conclusions: Absence of training-related data; low study power for some exposure variables. Conclusions: More extensive early-life turn out practices and later weaning enhanced later-life race performance outcomes. This could be due to increased opportunity for positive musculoskeletal tissue adaptation and optimal growth and development rates during a critical window of developmental plasticity. Unassigned: Expositionen während der Trächtigkeit und frühen Lebensphasen können die Entwicklung während des Wachstums und die zukünftige sportliche Leistungsfähigkeit beeifnflussen. Unassigned: Untersuchung von Zusammenhängen zwischen pränatalen und früher Expositionen bei Vollblütern und (i) der Wahrscheinlichkeit zu starten, (ii) der Gesamtanzahl an Rennen sowie (iii) dem insgesamt erzielten Preisgeld bis zum Ende des dritten Lebensjahres. Methods: Prospektive Kohortenstudie. Methods: Für 129 Vollblutfohlen auf sechs Gestüten wurden tägliche Aufzeichnungen zur Auslaufdauer und ‐fläche, Haltung sowie tierärztlich betreuten Erkrankungs‐ und Verletzungsereignissen von der Geburt bis zum Verlassen des Gestüts bzw. Studienaustritt geführt. Parallel wurden Angaben zur Abstammung sowie zur reproduktiven und trächtigkeitsbezogenen Gesundheit der Mütter erfasst. Leistungsdaten bis zum Ende des vierten Lebensjahres wurden aus brancheneigenen Datenbanken gesammelt. Zur Untersuchung der Zusammenhänge zwischen Expositionen und Leistungsparametern wurden gemischte logistische und lineare Regressionsmodelle mit Farm, Stute und Hengst als Zufallseffekte verwendet. Results: Insgesamt starteten 76 % der Pferde (98/129, 95 %‐KI: 68–82), mit einer Mediananzahl von 7 Rennen (IQR 4–11, Spanne 1–23) und einem Medianpreisgeld von £6.898 (IQR 1.712–17.987, Spanne 0–197.601). Eine längere durchschnittliche tägliche Auslaufzeit (in Stunden) und größere Auslauffläche (in Acres) in den ersten 6 Lebensmonaten waren mit einer erhöhten Wahrscheinlichkeit zu starten bzw. mit höherem erzieltem Preisgeld assoziiert (OR 1,31, 95 %‐KI: 1,09–1,58, P=0,004 und β‐Koeffizient=0,32 (lnGBP), 95 %‐KI: 0,03–0,61, P=0,03). Ein höheres Absetzalter (in Tagen) war mit einer erhöhten Startwahrscheinlichkeit sowie einer höheren Anzahl an Rennen verbunden (OR 1,03, 95 %‐KI: 1,01–1,05 und β‐Koeffizient=0,09, 95 %‐KI: 0,04–0,14, jeweils P<0,05).
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
Publication Date: 2025-08-25 PubMed ID: 40851510DOI: 10.1111/evj.70084Google Scholar: Lookup
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Summary
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Overview
- This study explored how conditions and exposures during gestation and early life affect the racing performance of Thoroughbred horses by age three, focusing on racing participation, number of starts, and total earnings.
- Key findings indicate that more daily turnout time, larger turnout areas, and later weaning are linked to better racing outcomes, possibly by promoting optimal musculoskeletal development during critical growth periods.
Background and Objective
- Gestational and early-life environments are crucial for developing tissues and systems that influence later athletic abilities.
- The researchers aimed to assess whether variables such as turnout management, health during early life, and maternal reproductive history are associated with the likelihood of a Thoroughbred racing, how many races it runs, and how much prizemoney it earns by the end of its third year.
Study Design and Methods
- Type of study: Prospective cohort study tracking foals from birth until they left the farm or the study ended.
- Subjects: 129 Thoroughbred foals from six different stud farms.
- Data collected:
- Daily records on turnout: how long horses spent outside and the size of the turnout area during the first 6 months.
- Management practices and records of veterinary-treated diseases or injuries during early life.
- Maternal health, reproductive records, and breed information collected in parallel.
- Racing data up to the end of the fourth year of life from official industry databases, including racing status, number of races, and prize money earned.
- Statistical analysis:
- Used mixed-effects logistic regression for the binary outcome of whether a horse raced or not.
- Used linear regression models for continuous outcomes: total number of runs and total prizemoney.
- Random effects included farm, mare, and stallion to account for clustering and shared genetics or environment.
Key Results
- Racing participation: 76% of foals (98/129) started in at least one race.
- Performance summary:
- Median number of races per horse: 7 (range: 1–23).
- Median prizemoney earned: £6898 (ranging from 0 to £197,601).
- Turnout duration: Greater average daily turnout time (in hours) during the first 6 months was associated with a 31% increase in odds of participating in racing (OR 1.31, 95% CI 1.09–1.58, p=0.004).
- Turnout area size: Larger turnout areas (in acres) were associated with increased total prizemoney earned (β-coefficient = 0.32 on the natural log scale of GBP, 95% CI 0.03–0.61, p=0.03).
- Age at weaning: Later weaning age in days was linked to increased odds of racing (OR 1.03 per day delay, 95% CI 1.01–1.05) and a higher total number of race starts (β = 0.09, 95% CI 0.04–0.14), both statistically significant.
Interpretation and Conclusions
- Early-life management practices that provide more opportunities for turnout—both in duration and space—seem to benefit the future athletic performance of Thoroughbreds.
- Later weaning might support better performance, possibly through extended maternal nutrition or social factors influencing development.
- The mechanisms likely involve enhanced musculoskeletal adaptation and healthier growth trajectories during a “window of developmental plasticity” when tissue growth is highly responsive to environmental stimuli.
- The absence of training data in the study is a limitation, as training intensity and quality could also influence performance outcomes.
- Some analyses had low statistical power, so findings should be confirmed with larger populations.
Significance for Thoroughbred Breeding and Training
- Management decisions in the first six months—including allowing more daily turnout hours in larger spaces and careful timing of weaning—could be critical for optimizing future racehorse performance.
- This suggests that attention to early-life environmental factors could complement genetic selection in improving racing success.
- Further research incorporating training regimen data and long-term follow-up would be valuable to refine recommendations.
Cite This Article
APA
Mouncey R, de Mestre AM, Arango-Sabogal JC, Verheyen KL.
(2025).
Born to run? Associations between gestational and early-life exposures and later-life performance outcomes in Thoroughbreds.
Equine Vet J.
https://doi.org/10.1111/evj.70084 Publication
Researcher Affiliations
- Department of Pathobiology and Population Sciences, Royal Veterinary College, Hatfield, UK.
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
- Département de pathologie et microbiologie, Faculté de médecine vétérinaire, Université de Montréal, Quebec, Canada.
- Department of Pathobiology and Population Sciences, Royal Veterinary College, Hatfield, UK.
Grant Funding
- EPDF 2022-9 / Horserace Betting Levy Board
- VET/PRJ/791 / Horserace Betting Levy Board
- Racing Foundation
- Royal Veterinary College's Mellon Fund for Equine Research
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